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  1. #1
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    Another little helmet light

    I'm almost embarrassed to post this, after the recent unveiling of Troutie's quad MC-E retina burner and Cloggy's magnificent home-brewed driver/pcb for his triple MC-E. Nothing groundbreaking here, just my first DIY led bike light (but not my last....I've already got parts stockpiled for at least a couple more ideas). So......

    What I wanted was a really small, lightweight helmet light that was brighter than my TR-801 torch, and didn't cost much to build. And maybe a little different than the others out there. What I think I've done here is crossbred an Amoeba with a double DIY Dinotte. (I hope that doesn't break any scientific ethical standards!). If you take two of the DX1920 8 optics, two Cree Q5s, two DX 3256 drivers, a couple switches and some wire and stuff it all into a pair of 3/4" (19mm) square aluminum tubes, here's what you get:
    (my apologies for the crappy cell phone photos....my camera should be back from warranty repair soon, I hope.)





    It's about 2.25" (57mm) long x 1.5" (38mm) x .75" (19mm). I finished it a couple weeks ago, but I've just figured how to free the photos from my phone (pay a 25 per photo ransom to Verizon Wireless The lighthead weighs 1.75 oz. (50 grams). Cost came to under $30 (US) for the parts. Of course my total expense was more, since the aluminum comes in 4' sections, DX drivers and optics come in multiples of 4 or 5, and I needed to buy things like AAA and epoxy. But that just means I'm well stocked for future builds

    I started with two 2" long pieces of Al tubing. I needed something to mount the led stars to that would conduct the heat to the outside, so I cut two squares of 1/4" (6.5mm) Al for heatsinks. This was probably the trickiest part of the build....getting the squares to fit perfectly in the tubing, and setting them at the exact correct depth to work with the optics. I came up with a method of using two wooden spacer blocks to get it right. Here's an exploded view, before assembly (and a completed tube on top, drilled for the led wires).



    The long spacer goes in first, from the back. Spread a thin band of AAA inside the tubing right above the spacer. Then press in the 1/4" Al heatsink (press harder, it's a tight fit!), then the other spacer, and clamp it up.



    If you remembered to wax the spacers before assembly, they should come right out. Theoretically. Even with wax, I had to drive a small screw into the blocks and pull with pliers to free them. I then drilled through the heatsinks for led wiring, and joined the tubes side by side with JB Weld epoxy.



    Once that was cured I got out the Dremel Tool and cut a notch out of the rear center wall, so wiring could pass between tubes. Then sand the epoxy seam flush, soften the sharp edges and corners, and sand to a 600 grit finish



    Next the optics had to be modified to fit into the square tubing. My original plan was to set the optics without the holders in silicone (they fit the i.d. of the tubing well). But Znomit proved to us that this is a bad idea, and Salty suggested that it was easy to mod the holders. It was easier than I could have hoped. I took a piece of the square tubing and pressed it down over the cone of the holder, leaving marks in the plastic. With a razor knife it was very easy to cut small notches so the holder would go into the tubing up to it's front ring. Then I put the holder face down with the square tubing over it and made a straight cut flush with one side. Then pop in the optic and a couple swipes with sandpaper flushes the optic with the cut side.
    An un-modded optic on the left, middle is notched, right has the flat cut:



    I installed the leds the same way Troutie did on his "insane quad MC-E": put the leds in their holders, a thin coat of AAA on the back of the stars, then press the holders into the case. It worked great. I had soldered the leads onto the stars and threaded them through the heatsink in this step too.....made that step in the soldering easier.



    Time to wire it up. I found some plastic end caps at the hardware store that fit the tubing. And some switches at Radio Shack that fit the end caps. The positive lead from the battery goes to both switches, then to the central (+) pads on the underside of the 3256 drivers. Negative battery lead goes to the driver's (-) pads (anywhere on the underside outer ring). The led (+) and (-) leads go to the appropriate points on the other side of the drivers. Hook up the battery, flip the switches, and if everything is right, it lights. It does!



    I put several coats of liquid electrical tape over all my solder connections, and around the outer edge of the driver boards, to prevent shorts to the aluminum case. Then carefully stuffed it all into the tubes, put a bead of silicone inside the ends of the tubes, and pressed in the end caps.

    All that was left was to pull out the optic holders and reinstall with a bead of silicone, and then install the optics into the holders, with the tiniest bead of silicone, just on the flange (I promise!) to seal it

    It works great. Theoretically it should be putting out over 400 lumens. It certainly looks twice as bright as my TR-801 torch. I'm running it on 4 AAs. With both leds lit, standard NiMH 2500mAh AAs gave me 1.5 hours of light but the batteries were getting warm....apparently not good. With Eneloop 2000mAh AAs I get over an hour before it starts dimming, and the batteries are happy. I'm going to hack an 8 x AA holder into 4s2p configuration; that will give me 4000mAh and over 2 hours....and even more since I can switch off one led on the slow climbs.

    Whew! That was a long post for such a little light....thanks for reading along, and I hope you've enjoyed the show! I sure have...now on to the next light

    JZ

  2. #2
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    Nice light and excellent write up .

    It looks like you enjoyed the process and hopefully you'll enjoyed the light as much.
    When you think that life is though, keep a positive attitude : remember that it is short ;-)

  3. #3
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    JZ, that's a nice little light and with a driver per LED you won't be left in the dark if one was to fail.

    What sort of mount will you use?

  4. #4
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    Excellent work

    Did you happen to measure the current coming from the driver board?

    Also what kind of voltage are you getting from the batteries (and what kind of pack are you using?)
    We can bomb the world to pieces, but we can't bomb it into peace -Michael Franti

  5. #5
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    Quote Originally Posted by yetibetty
    What sort of mount will you use?
    I was going to try the industrial-strength velcro on the underside like Scar uses on his Amoeba. Although something that would allow airflow around all 4 sides of the case might be better. With such a small case it depends entirely on airflow for cooling....it gets pretty warm in still 68F air.

    I'm open to suggestions. Maybe an aluminum U-channel with one leg AAAed to the bottom, and the other velcro-strapped to the helmet. That would add some heatsink surface too.

    If I build more of these (there's some interest from friends and family) I'll probably cut grooves lengthwise in the case for added surface area.

    JZ
    It's not about speed, it's about lack of control.

  6. #6
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    Quote Originally Posted by kuksul08
    Excellent work

    Did you happen to measure the current coming from the driver board?

    Also what kind of voltage are you getting from the batteries (and what kind of pack are you using?)
    I had read that these drivers can vary a little, so I did test them before installation.....they measured just over 900mA

    I have a 4 x AA Eneloop pack right now 4.8v nominal, 2000mAh. Four "regular" NiMH AAs couldn't handle the current draw. There's a discussion of the battery performance of this light in the Battery voltage under load thread.

    JZ
    It's not about speed, it's about lack of control.

  7. #7
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    Very nice little light and well made .
    no embarasment required

    and Cool write up and pics

    An early trout lite

  8. #8
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    Quote Originally Posted by JimZinVT
    I had read that these drivers can vary a little, so I did test them before installation.....they measured just over 900mA

    I have a 4 x AA Eneloop pack right now 4.8v nominal, 2000mAh. Four "regular" NiMH AAs couldn't handle the current draw. There's a discussion of the battery performance of this light in the Battery voltage under load thread.

    JZ

    Thanks for the link

    I hadn't even put too much thought into the load voltage of the batteries. I have some Panasonic NiMH's that I have had for a long time. I have a feeling they are good quality though, because after years they still read 1.41V off the charger, and have a low discharge rate.
    The plan was to use 8s2p configuration connected to two LEDs drawing a total of 1.4A. So hopefully each battery can handle 700mA current.
    We can bomb the world to pieces, but we can't bomb it into peace -Michael Franti

  9. #9
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    Quote Originally Posted by JimZinVT
    I was going to try the industrial-strength velcro on the underside like Scar uses on his Amoeba. Although something that would allow airflow around all 4 sides of the case might be better. With such a small case it depends entirely on airflow for cooling....it gets pretty warm in still 68F air.

    I'm open to suggestions. Maybe an aluminum U-channel with one leg AAAed to the bottom, and the other velcro-strapped to the helmet. That would add some heatsink surface too.

    If I build more of these (there's some interest from friends and family) I'll probably cut grooves lengthwise in the case for added surface area.

    JZ
    I quite like the "L" (angle?) that Cytoe used. Or you could just buy a Cateye helmet mount and spacer.
    Last edited by yetibetty; 03-23-2009 at 10:23 AM.

  10. #10
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    Good looking light there. Spacers are a great idea. I just eyeball all mine. Sometimes it shows.

  11. #11
    Feet back and spread 'em!
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    very clean execution JimZin and the step-by step is appreciated.....noob question: what is AAA (other than anti-aircraft artillery). thx
    the time is right for violent revolution

  12. #12
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    Quote Originally Posted by JimZinVT
    I
    I'm open to suggestions. Maybe an aluminum U-channel with one leg AAAed to the bottom, and the other velcro-strapped to the helmet. That would add some heatsink surface too.
    JZ
    How about the U channel upside down and slots cut in the legs for the strap would definatly sit better on my giro lid
    and give you the stand off and you could chuck a finned memory heatsink in there too

    Bikecop AAA is Arctic alumina epoxy adhesive specially for heat transfer

  13. #13
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    Looking really good there Jim. Nice work.

  14. #14
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    Nice work Jim!

    It reminds me of my little Altoid light. 400+ lumens in an easy package. Looks a lot more professional than mine.

    The 2 driver solution for the small battery pack is nice.

    I've been using mine for snow shoeing at night. Too much snow for biking! Skiing has been great!

  15. #15
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    Quote Originally Posted by troutie-mtb
    How about the U channel upside down and slots cut in the legs for the strap would definatly sit better on my giro lid
    and give you the stand off and you could chuck a finned memory heatsink in there too

    Bikecop AAA is Arctic alumina epoxy adhesive specially for heat transfer
    JimZin: here's how I used a bit of spare u-channel to mount my triple to my helmet...works a treat!!
    Attached Images Attached Images

  16. #16
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    Nice. Similar to what you've got under the Trout/Deesta 6 x XPEe collaboration too.

    I'd like to get it up off the helmet further, so my finless housing gets airflow underneath too. I'm thinking a piece of 1" x 1" U-channel, with the open end forward. A velcro strap will secure the base leg to the helmet, and maybe drill the vertical leg to shave a little weight and add a little surface area. Should work and maybe even look cool

    If I build more of these little lights I'm definitely going to cut fins in the housing.

    JZ
    It's not about speed, it's about lack of control.

  17. #17
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    Thanks for sharing, it looks an excellent light.

    Am I correct in assuming that you have sealed the optic holders into the square section with silicone. If so was it difficult to seal the corners?

    Thanks

    Pete

  18. #18
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    Pete: Yes, high temp silicone between the optic holder and the case. I put a bead of silicone around the inside of the front of the square tubing, and an extra blob in the corners where the holder doesn't have full contact, and pressed them in. It should be a good seal, but I haven't done any undersea testing A very fine bead of clear silicone seals the optic to the holder.

    JZ
    It's not about speed, it's about lack of control.

  19. #19
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    Quote Originally Posted by JimZinVT
    I'd like to get it up off the helmet further, so my finless housing gets airflow underneath too. I'm thinking a piece of 1" x 1" U-channel, with the open end forward.
    I started and then scrapped this idea tonight....would be too tall and a serious branch-catcher. Going with something lower profile, similar to what Deesta and Troutie described.

    JZ

  20. #20
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    Scar runs his at 800 mA with less surface area. The Amoeba is 1.5 by 1.5 inches. I have the spot and the flood. Never had heat issues this summer in Texas. Often in the 90's at night here. Feels good compared to the 100 plus daytime temps.
    Just saying. Run without the fins until you find that you need them.

  21. #21
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    od: are you using the velcro mount on your Amoebas? How's that working? I was worried the warmth of the light would soften the adhesive. but scar's been selling that setup for a while, so the "industrial" velcro must have a burlier adhesive.

    90 at night....wow, that's 120 warmer than what we had a couple weeks ago! (where's the "shivering" smiley?) I'm not sure which is worse.

    JZ

  22. #22
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    Scar uses some nice velcro. Never had any issue with his. I use velcro on my lights as well. Holds most of the time. If it gives me trouble I add some Gorilla Glue. That fixes it forever.
    It is really hot, even at night, here during the summer. The Amoeba lights never had any issue with the ambient temperatures.
    It was only around 50 degrees here tonight. Felt great. Ran into about 7 piglets on the trail. One squealed like I ran it over and its mother seemed to find my presence offensive. Needless to say I got out of there fast. Amazing the speed you can find when a PO'ed sow is crashing towards you in the dark.

  23. #23
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    Just about to order some parts from DX, thier CREE Q5's on 14mm bases are WC's. Some people on the forums have suggested that WGs are more daylight like.

    Any thoughts out there?

    Thanks

    Pete

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